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use crate::io::util::chain::{chain, Chain};
use crate::io::util::read::{read, Read};
use crate::io::util::read_exact::{read_exact, ReadExact};
use crate::io::util::read_to_end::{read_to_end, ReadToEnd};
use crate::io::util::read_to_string::{read_to_string, ReadToString};
use crate::io::util::take::{take, Take};
use crate::io::AsyncRead;
cfg_io_util! {
/// Read bytes from a source.
///
/// Implemented as an extention trait, adding utility methods to all
/// [`AsyncRead`] types. Callers will tend to import this trait instead of
/// [`AsyncRead`].
///
/// As a convenience, this trait may be imported using the [`prelude`]:
///
/// ```no_run
/// use tokio::fs::File;
/// use tokio::prelude::*;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let mut f = File::open("foo.txt").await?;
/// let mut buffer = [0; 10];
///
/// // The `read` method is defined by this trait.
/// let n = f.read(&mut buffer[..]).await?;
///
/// Ok(())
/// }
/// ```
///
/// See [module][crate::io] documentation for more details.
///
/// [`AsyncRead`]: AsyncRead
/// [`prelude`]: crate::prelude
pub trait AsyncReadExt: AsyncRead {
/// Create a new `AsyncRead` instance that chains this stream with
/// `next`.
///
/// The returned `AsyncRead` instance will first read all bytes from this object
/// until EOF is encountered. Afterwards the output is equivalent to the
/// output of `next`.
///
/// # Examples
///
/// [`File`][crate::fs::File]s implement `AsyncRead`:
///
/// ```no_run
/// use tokio::fs::File;
/// use tokio::io::{self, AsyncReadExt};
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let f1 = File::open("foo.txt").await?;
/// let f2 = File::open("bar.txt").await?;
///
/// let mut handle = f1.chain(f2);
/// let mut buffer = String::new();
///
/// // read the value into a String. We could use any AsyncRead
/// // method here, this is just one example.
/// handle.read_to_string(&mut buffer).await?;
/// Ok(())
/// }
/// ```
fn chain<R>(self, next: R) -> Chain<Self, R>
where
Self: Sized,
R: AsyncRead,
{
chain(self, next)
}
/// Pull some bytes from this source into the specified buffer,
/// returning how many bytes were read.
///
/// Equivalent to:
///
/// ```ignore
/// async fn read(&mut self, buf: &mut [u8]) -> io::Result<usize>;
/// ```
///
/// This function does not provide any guarantees about whether it
/// completes immediately or asynchronously
///
/// If the return value of this method is `Ok(n)`, then it must be
/// guaranteed that `0 <= n <= buf.len()`. A nonzero `n` value indicates
/// that the buffer `buf` has been filled in with `n` bytes of data from
/// this source. If `n` is `0`, then it can indicate one of two
/// scenarios:
///
/// 1. This reader has reached its "end of file" and will likely no longer
/// be able to produce bytes. Note that this does not mean that the
/// reader will *always* no longer be able to produce bytes.
/// 2. The buffer specified was 0 bytes in length.
///
/// No guarantees are provided about the contents of `buf` when this
/// function is called, implementations cannot rely on any property of the
/// contents of `buf` being true. It is recommended that *implementations*
/// only write data to `buf` instead of reading its contents.
///
/// Correspondingly, however, *callers* of this method may not assume
/// any guarantees about how the implementation uses `buf`. It is
/// possible that the code that's supposed to write to the buffer might
/// also read from it. It is your responsibility to make sure that `buf`
/// is initialized before calling `read`.
///
/// # Errors
///
/// If this function encounters any form of I/O or other error, an error
/// variant will be returned. If an error is returned then it must be
/// guaranteed that no bytes were read.
///
/// # Examples
///
/// [`File`][crate::fs::File]s implement `Read`:
///
/// ```no_run
/// use tokio::fs::File;
/// use tokio::io::{self, AsyncReadExt};
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let mut f = File::open("foo.txt").await?;
/// let mut buffer = [0; 10];
///
/// // read up to 10 bytes
/// let n = f.read(&mut buffer[..]).await?;
///
/// println!("The bytes: {:?}", &buffer[..n]);
/// Ok(())
/// }
/// ```
fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Read<'a, Self>
where
Self: Unpin,
{
read(self, buf)
}
/// Read the exact number of bytes required to fill `buf`.
///
/// Equivalent to:
///
/// ```ignore
/// async fn read_exact(&mut self, buf: &mut [u8]) -> io::Result<usize>;
/// ```
///
/// This function reads as many bytes as necessary to completely fill
/// the specified buffer `buf`.
///
/// No guarantees are provided about the contents of `buf` when this
/// function is called, implementations cannot rely on any property of
/// the contents of `buf` being true. It is recommended that
/// implementations only write data to `buf` instead of reading its
/// contents.
///
/// # Errors
///
/// If the operation encounters an "end of file" before completely
/// filling the buffer, it returns an error of the kind
/// [`ErrorKind::UnexpectedEof`]. The contents of `buf` are unspecified
/// in this case.
///
/// If any other read error is encountered then the operation
/// immediately returns. The contents of `buf` are unspecified in this
/// case.
///
/// If this operation returns an error, it is unspecified how many bytes
/// it has read, but it will never read more than would be necessary to
/// completely fill the buffer.
///
/// # Examples
///
/// [`File`][crate::fs::File]s implement `Read`:
///
/// ```no_run
/// use tokio::fs::File;
/// use tokio::io::{self, AsyncReadExt};
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let mut f = File::open("foo.txt").await?;
/// let mut buffer = [0; 10];
///
/// // read exactly 10 bytes
/// f.read_exact(&mut buffer).await?;
/// Ok(())
/// }
/// ```
///
/// [`ErrorKind::UnexpectedEof`]: std::io::ErrorKind::UnexpectedEof
fn read_exact<'a>(&'a mut self, buf: &'a mut [u8]) -> ReadExact<'a, Self>
where
Self: Unpin,
{
read_exact(self, buf)
}
/// Read all bytes until EOF in this source, placing them into `buf`.
///
/// Equivalent to:
///
/// ```ignore
/// async fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize>;
/// ```
///
/// All bytes read from this source will be appended to the specified
/// buffer `buf`. This function will continuously call [`read()`] to
/// append more data to `buf` until [`read()`][read] returns `Ok(0)`.
///
/// If successful, the total number of bytes read is returned.
///
/// # Errors
///
/// If a read error is encountered then the `read_to_end` operation
/// immediately completes. Any bytes which have already been read will
/// be appended to `buf`.
///
/// # Examples
///
/// [`File`][crate::fs::File]s implement `Read`:
///
/// ```no_run
/// use tokio::io::{self, AsyncReadExt};
/// use tokio::fs::File;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let mut f = File::open("foo.txt").await?;
/// let mut buffer = Vec::new();
///
/// // read the whole file
/// f.read_to_end(&mut buffer).await?;
/// Ok(())
/// }
/// ```
///
/// (See also the [`tokio::fs::read`] convenience function for reading from a
/// file.)
///
/// [`tokio::fs::read`]: crate::fs::read::read
fn read_to_end<'a>(&'a mut self, buf: &'a mut Vec<u8>) -> ReadToEnd<'a, Self>
where
Self: Unpin,
{
read_to_end(self, buf)
}
/// Read all bytes until EOF in this source, appending them to `buf`.
///
/// Equivalent to:
///
/// ```ignore
/// async fn read_to_string(&mut self, buf: &mut String) -> io::Result<usize>;
/// ```
///
/// If successful, the number of bytes which were read and appended to
/// `buf` is returned.
///
/// # Errors
///
/// If the data in this stream is *not* valid UTF-8 then an error is
/// returned and `buf` is unchanged.
///
/// See [`read_to_end`][AsyncReadExt::read_to_end] for other error semantics.
///
/// # Examples
///
/// [`File`][crate::fs::File]s implement `Read`:
///
/// ```no_run
/// use tokio::io::{self, AsyncReadExt};
/// use tokio::fs::File;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let mut f = File::open("foo.txt").await?;
/// let mut buffer = String::new();
///
/// f.read_to_string(&mut buffer).await?;
/// Ok(())
/// }
/// ```
///
/// (See also the [`crate::fs::read_to_string`] convenience function for
/// reading from a file.)
///
/// [`crate::fs::read_to_string`]: crate::fs::read_to_string::read_to_string
fn read_to_string<'a>(&'a mut self, dst: &'a mut String) -> ReadToString<'a, Self>
where
Self: Unpin,
{
read_to_string(self, dst)
}
/// Creates an adaptor which reads at most `limit` bytes from it.
///
/// This function returns a new instance of `AsyncRead` which will read
/// at most `limit` bytes, after which it will always return EOF
/// (`Ok(0)`). Any read errors will not count towards the number of
/// bytes read and future calls to [`read()`][read] may succeed.
///
/// # Examples
///
/// [`File`][crate::fs::File]s implement `Read`:
///
/// ```no_run
/// use tokio::io::{self, AsyncReadExt};
/// use tokio::fs::File;
///
/// #[tokio::main]
/// async fn main() -> io::Result<()> {
/// let f = File::open("foo.txt").await?;
/// let mut buffer = [0; 5];
///
/// // read at most five bytes
/// let mut handle = f.take(5);
///
/// handle.read(&mut buffer).await?;
/// Ok(())
/// }
/// ```
fn take(self, limit: u64) -> Take<Self>
where
Self: Sized,
{
take(self, limit)
}
}
}
impl<R: AsyncRead + ?Sized> AsyncReadExt for R {}